YALE (US) — When it comes to ants and energy usage, big and mean beats small and green.

Scientists had believed that, at the population level at least, the body size of individuals makes no difference in the amount of energy used.

Small individuals use less energy, but tend to be more numerous than large individuals, who generally use more, so at the population level, size and abundance were thought to cancel each other out. Energy use then works out to be the same.

But when actually tested, the energy equivalence rule proved wrong—at least with insect colonies, according to a new study published in the journal Biology Letters.

Colonies of large ants use more energy as measured in metabolic rates than colonies made up of smaller ants, giving larger species an ecological and evolutionary leg up, says John DeLong of Yale University’s department of ecology and evolutionary biology.

“The process seems to be that as individuals get bigger, they are more successful at obtaining resources, which creates a positive feedback that allows for colony expansion,” DeLong says.